The idea for the seemingly inconsequential digital thumbs-up icon we know as the Like button emerged around 1995 and had unexpectedly momentous consequences. Today, we click the Like button more times per day than there are people on the planet. The button facilitates human interactions, feeds us information, and helps us build connections online. But what accounts for its meteoric rise? And why did its success surprise even its creators? To answer these questions and more, we set about writing Like: The Button That Changed the World.
It’s hard to say who invented the Like button, since many people in Silicon Valley in the early 2000s were working simultaneously on a related set of challenges—such as how to rank content or encourage restaurant reviews—in an environment where informal sharing and learning across companies was common. One surprising discovery in our interviews with the pioneers of the Like button, such as James Hong, a co-founder of Hot or Not, an attractiveness-rating site, and Biz Stone, a co-founder of Twitter, was that none of them foresaw its eventual consequences—or even regarded it at the time as more than a quick fix to one of the countless tactical-design problems they faced daily. That in itself was startling: something so world-changing, born out of a moment of routine problem-solving.
In addition to taking notes from each other, these early pioneers were also influenced by a book popular among Web designers and engineers at the time: Don’t Make Me Think, by Steve Krug. Its central idea was that in order for innovations to spread virally, they should not seem novel or require any special effort from users. That, too, astonished us in hindsight: the Like button’s success came not from its novelty but from its familiarity. It never required instructions—instead, it tapped into a deep human instinct that was already there.
Over the course of our research, we also learned the extent to which the Like button mirrors our neurological wiring. Studies of brain chemistry and anatomy confirm that the frisson—the release of dopamine in the nucleus accumbens—we experience when liking or being liked on social media is the same mechanism that rewards real-world pleasures such as social interaction or sex. The Like button, it turns out, stimulates ancient evolutionary circuits tied to our survival instincts and social behavior.
According to the Yale sociologist and physician Nicholas Christakis, the Like button rewards a “social suite” of behaviors related to the human superpower of social learning. One of the tendencies in this social suite is homophily—our preference for associating with and learning from people similar to ourselves. Homophily has a very powerful influence over humans: In the social-media realm, this means we tend to seek out content that appeases our existing preferences. By clicking the Thumbs-up button, users can signal that they not only like someone else’s content but that they are also like them—double homophily.
Another element of the social suite is our preference for mild hierarchy. Unlike dominance hierarchies in the animal world, such as those within groups of primates, in which order is decided based on aggression and physical violence, humans tend to gravitate toward individuals who are popular and have social power and influence. The thumbs-up symbol and its associated tally of likes subtly supports this tendency, providing a visible cue of social endorsement.
At the same time, this symbol of affirmation has led to unintended negative consequences like social-media addiction and self-esteem issues in children. One of the biggest revelations in our research was learning that the difference between online and real-life validation is in the scale. Real-world social interactions are limited by time, distance, and other physical constraints. But digital likes can be given in vast quantities, and at high frequencies. This influx overloads the dopamine circuits, especially in young, developing brains. Ironically, by following the dictum of Don’t Make Me Think, the designers of the Like button created something so frictionless that it could overwhelm the very instincts it tapped into.
Perhaps the most surprising finding of all: None of this was intended. As with many technologies, neither the benefits nor the drawbacks of digital liking were foreseen by its pioneers.
As the next technological wave—A.I.—takes off, the 30-year history of the humble Like button has much to teach us about how innovation really works: not as a clean, linear process but as a messy, unexpected, and deeply social one.
Martin Reeves is the chairman of the Boston Consulting Group’s Henderson Institute think tank
Bob Goodson was the first employee at Yelp and is a co-founder and the C.E.O. of Quid
